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The coronavirus pandemic was about to happen, according to a new study, cited by CNN. Researchers studying when and how the virus appeared in China calculated that the first human infection occurred as early as October 2019. Furthermore, their model showed something else: the virus had little chance of triggering a pandemic.
Only bad luck and a combination of conditions in Wuhan’s Huanan food market gave the virus the impetus it needed to spread globally, the researchers wrote in the study published in the journal Science.
“It was the perfect storm, we now know that the virus needed a gap or two to spread that way,” said Michael Worobey, a professor of evolutionary biology at the University of Arizona who was involved in the study.
“If things had been very little different, if the person who brought the virus to the Wuhan market had decided not to go that day or if they had been too sick to leave home, the spread would probably not take place. Maybe we never would have known, ”he added.
The first infections, at the earliest in October 2019
The research team performed molecular dating, using the rate of mutations in the virus to calculate how long it has been around. Scientists have also developed mathematical models to explain how and when it spread.
“Our study looked at how long the SARS-CoV-2 virus had been circulating in China before it was discovered,” said Joel Wertheim, associate professor of infectious diseases at the University of California.
“To answer this question, we combined three important pieces of information: how the virus spread in Wuhan before the lockdown, the genetic diversity of the virus in China, and data on the first COVID cases in China. By combining this information, we were able to establish in mid-October 2019 as the deadline for the virus to start circulating in Hubei province ”.
Current evidence indicates that the virus could not have circulated before then, say the researchers, who are skeptical about the existence of COVID cases outside of China at the time.
The study also shows that the virus appeared in Hubei province in China, not elsewhere.
Of some cases here and there in late 2019, the virus has “exploded” globally. So far, more than 120 million cases of illness and nearly 2.7 million deaths have been reported.
The study does not determine which animal harbored the virus. Genetic evidence indicates that bats carry a close variant of the virus and that another animal has mediated transmission of the virus to humans.
One in three chances of a pandemic
The US Centers for Disease Control and Prevention frequently find new strains of the flu in people who go to outdoor fairs and interact with pigs, for example. But so far none of these infections has turned into an epidemic or even a pandemic.
This requires an infected person to have a lot of contact with other people, such as a congested food market.
“If the virus is not so lucky to meet these conditions, even a well-adapted virus can disappear,” said Worobey.
“This gives it a different perspective: These events probably happen much more often than we know. It’s just that they just don’t have that purpose and we never find out about them.”
Instead, it happened with COVID-19.
In the researchers’ mathematical models, the virus developed in the pandemic in only 30% of the simulations. In other cases, the virus simply disappeared after infecting some people.
“What happened here: The virus infected a small number of people in October, November and December 2019, until it reached the Wuhan food market,” Worobey explained.
The market is likely not the place where the first infection occurred, but the place where infections multiplied.
The advantage of not being lethal
Given the very short period of time since the vius appeared, it’s remarkable that it has been identified so quickly, Worobey said. In December 2019 the possibility of discovering a new virus was discussed, and by January 2020 it had already been sequenced and characterized.
However, it was too late, probably because the virus is not lethal enough. The first SARS virus killed approximately 10% of its victims during the 2002-2004 pandemic, which was stopped by a concerted global effort.
“We, the scientific community, were aware of the pandemic potential of a moderately virulent but highly transmissible pathogen. But our disease notification system is conditional on the detection of viruses in hospitalized or deceased patients. Clearly, this was not enough to stop COVID-19, “Joel Wertheim told CNN.
Editing: Bogdan Pacurar
